The present invention relates generally to the transport and handling of articles being subjected to vacuum processes, and, more specifically, to the transport and handling of integrated circuit wafers being processed in vacuum chambers, such as by evaporation, vapor deposition, sputtering, plasma etching and the like.
Integrated circuits, most commonly formed on either silicon (Si) semiconductor or gallium arsenide (GaAs) wafer substrates, are commonly subjected to one or more process steps within a vacuum chamber in the course of forming a large number of replicas of an integrated circuit on each wafer. In order to avoid having to vent the vacuum processing chamber each time one or more wafers is loaded into or removed from the processing chamber, and then re-establish a vacuum before processing can begin, the wafers are moved through an intermediate load lock chamber. The load lock chamber is connected to the vacuum chamber through a gate valve, and has another gate valve opening to the outside. The pressure within the load lock chamber is controllable independently of that in the processing chamber.
Wafers or other articles to be processed are loaded into the processing chamber by first moving them into the load lock chamber through its outside gate valve while the gate valve connecting the two chambers remains closed. The processing chamber is maintained at or very near its processing pressure during loading and unloading. The outside gate valve is then closed with the articles in the load lock chamber, and the pressure within the load lock chamber is reduced to a level about equal to that of the vacuum chamber. The gate valve between the chambers is then opened and the articles moved into the processing chamber through that gate valve. This gate valve is then closed and the articles in the processing chamber are processed. These steps are performed in a reverse order when removing articles from the processing chamber to the outside through the load lock chamber. The load lock chamber is vented after the articles are moved into it from the processing chamber when the load lock chamber is at the reduced pressure of the processing chamber. Some vacuum processing machines have two load lock chambers connected by separate gate valves to the processing chamber in order to increase the throughput of wafers processed, one load lock chamber being used for loading and the other for unloading.